The 22ppcUSA is the factory cartridge based off the 22ppc which was a wildcat cartridge designed with short range Benchrest in mind. The two gentlemen, whose last names began with P's, derived it from the .220 Russian parent case and ended up dealing with SAKO of Finland for the rights to produce both cartridge and ammunition as the 22ppcUSA. I suspect the 22ppcSako is incorrect nomenclature for the 22ppcUSA whereas Sako was producing it. The 22ppc generally is a tight necked chamber which requires neck turning the brass whereas the 22ppcUSA is like every other factory cartridge with ample clearance for the case. The 22ppc quickly became the 6ppc to meet the caliber restriction thus allowing shooters to use one cartridge (and possibly one rifle) in all classes. I do not know if anyone is still producing factory ammo for the 22ppcUSA. Randy J.